As this kind of device, for example, there is proposed a device that makes a determination on a rough road on the basis of a result of a frequency analysis of a rotational speed of a crank angle sensor (see Patent Document 1). Alternatively, there is proposed a device that sets a flag when a state where a wheel acceleration/deceleration assumes a value equal to or larger than a set acceleration/deceleration has continued for, for example, 6 or more milliseconds, and determines that a vehicle travels on a rough road, when the flag is set a predetermined number of times or more within a set time (see Patent Document 2).